The present invention relates generally to a system for introducing a controlled gaseous mixture into an exposure chamber. More particularly, the present invention relates to a system for introducing a noxious gas into an exposure chamber containing plants which are to be exposed, under controlled conditions over long periods of time, to an atmospheric gas which is given a defined composition by the introduction of the noxious gas.
In such exposure chambers, climatic values and light are regulated electrically. The monitoring of operations and the introduction of the noxious gas is effected by means of a local computer network which monitors the chamber operation by means of a call service and regulates the introduction of noxious gas on the basis of a computer program. The desired functions and increased reliability must be realized by mechanical and electronic development. For example, it must be assured that the service operator on duty or any other authorized worker, is able to monitor the system's status by way of a computer voice output. This mode of operation must be made secure against unauthorized access to the computer since the voice channel does not permit any type of input. Moreover, the data collected at various locations in the chamber system must be transferred by the computer disposed at that location via the local network to a large or main memory. The entire local network, including the main memory, the electronic components of the network and the computers, must be secured against loss of current by means of an instantaneous current supply.
The routine data for regulating and monitoring are generally written in by means of an optical bar graph reader. A dot matrix printer is used to set up a table which contains all of the customary code combinations. Special functions are put in by means of a parallelly connected teletypewriter. This device additionally keeps a protocol of the bar graph signals in uncoded script.
An EEPROM programming circuit connected to the computer compiles, from the input data, an EEPROM which is inserted into the control computer for the chamber operating device. Typographical errors and double inputs are eliminated. For the compilation of measured data and the emission of control signals, a programmable data logger forms the connection between the respective computer on location with the control and measuring signal transducers. The system monitoring program and the noxious substance regulating or controlling program are subdivided into small portions which the data logger can handle and which are transferred to the data logger by the respective network computer at the points in time required by the operating sequence.
In a data logger, a compact device, the analog/digital converter is switched to the built-in computer in such a manner that the attachment of a peripheral device customary with universal devices does not take place. The data logger is galvanically separated from the computer by means of optical couplers. Batteries assure 18 hours of operation in the case of a malfunction of the electrical mains. The built-in magnetic tape cassette station, the built-in printer and the manual operation keyboard permit autonomous operation if there is a computer malfunction or for other reasons.
To alarm the control station, the data logger triggers a "dead man" circuit at two-minute intervals. If no signal appears, an alarm is initiated in the control station. The person on watch then informs the duty personnel for the chamber operation.
All of the above described complicated monitoring measures require a reliable gas supply to the exposure chamber, particularly if atmospheric gas is mixed with noxious gas(es). Providing the gas for days and months from gas bottles in which the prepared gas mixture is contained would be impossible here, at least for economic reasons, because of the multitude of bottles required and the change of bottles connected therewith.
Providing the gases in bottles containing the gas in a 100% concentration and mixing them on location is fraught with almost unsurmountable technical difficulties. For experiments which require very small concentrations, these 100% gases are barely manageable with the required accuracy by the standard control devices. Additionally, usable uniformity is very difficult to attain with very small drops of gas.
If commercially available regulators are used, each electrical interference would result in a great danger to the experimental material.